A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. IV. Effect of gamma irradiation on mechanical and material properties

Both Acetabular and Femoral Reconstructions With Impaction Bone Grafting in Revision Total Hip Arthroplasty: Case Series and Literature Review

Background

Extensive bone loss on femur and acetabulum posed a big challenge to orthopedists in total hip revision surgeries. Impaction bone grafting (IBG) as a valuable bone preservation technique could effectively address this problem. Either IBG revision on the femoral or acetabular side was well studied, while its use on both sides in one operation was not. The aim of this study is to present the outcomes of IBG on both femoral and acetabular sides at first-time hip revision.

Methods

We retrospectively reviewed 8 patients (mean follow-up of 5.8 years) undergoing first-time revision with IBG on both acetabular and femoral sides at our institution. The Paprosky classification system was used to classify bone defects. Freeze-dried allografts and cemented prostheses were used in all patients. Postoperative complications and rerevision rates were reported.

Results

Five patients presented a Paprosky type IIC acetabular defect, 3 with a type IIIB, IIIA, and IIC defect, respectively. Three patients presented with a type IV femoral defect, 3 with a type IIIB defect, and 2 with a type II defect. Two patients developed complications, while one had an intraoperative femoral fracture and one had delayed wound healing. At the latest follow-up, no patient had rerevisions or operations related to the prosthesis.

Conclusions

IBG in combination with cemented prosthesis is a profitable biological reconstruction revision technique that could provide satisfying midterm outcomes. We first propose the use of blood clots mixed with bone grafts for potential bone incorporation enhancement, while its specific effects need to be verified in further studies.

High-speed X-ray visualization of dynamic crack initiation and propagation in bone

The initiation and propagation of physiological cracks in porcine cortical and cancellous bone under high rate loading were visualized using high-speed synchrotron X-ray phase-contrast imaging (PCI) to characterize their fracture behaviors under dynamic loading conditions. A modified Kolsky compression bar was used to apply dynamic three-point flexural loadings on notched specimens and images of the fracture processes were recorded using a synchronized high-speed synchrotron X-ray imaging set-up. Three-dimensional synchrotron X-ray tomography was conducted to examine the initial microstructure of the bone before high-rate experiments. The experimental results showed that the locations of fracture initiations were not significantly different between the two types of bone. However, the crack velocities in cortical bone were higher than in cancellous bone. Crack deflections at osteonal cement lines, a prime toughening mechanism in bone at low rates, were observed in the cortical bone under dynamic loading in this study. Fracture toughening mechanisms, such as uncracked ligament bridging and bridging in crack wake were also observed for the two types of bone. The results also revealed that the fracture toughness of cortical bone was higher than cancellous bone. The crack was deflected to some extent at osteon cement line in cortical bone instead of comparatively penetrating straight through the microstructures in cancellous bone. STATEMENT OF SIGNIFICANCE: Fracture toughness is with great importance to study for crack risk prediction in bone. For those cracks in bone, most of them are associated with impact events, such as sport accidents. Consequently, we visualized, in real-time, the entire processes of dynamic fractures in notched cortical bone and cancellous bone specimens using synchrotron X-ray phase contrast imaging. The onset location of crack initiation was found independent on the bone type. We also found that, although the extent was diminished, crack deflections at osteon cement lines, a major toughening mechanism in transversely orientated cortical bone at quasi-static rate, were still played a role in resisting cracking in dynamically loaded specimen. These finding help researchers to understand the dynamic fracture behaviors in bone.

Effect of bone bank processing on bone mineral density, histomorphometry & biomechanical strength of retrieved femoral head

Background & objectives:

Standard processing of the bone grafts involves deep-freezing and sterilization with gamma irradiation which may alter mechanical properties of the bone graft. This study was aimed at measuring the effect of bone bank processing on the mechanical properties of bone allograft and its correlation with bone mineral density [BMD, dual-energy X-ray absorptiometry (DEXA Scan)] and histomorphometric indices.

Methods:

Femoral heads retrieved from patients undergoing hip replacement surgeries were used as the material. Twenty femoral heads were under taken in the study. Each femoral head was cut into two equal cubes. One cube was subjected to BMD measurement using DEXA Scan followed by unilateral compression test. Histomorphometric indices such as trabecular number (Tb. N.), trabecular separation (Tb. S.), trabecular thickness (Tb. T.) and bone volume (B.V.) were calculated on the same specimen by a computer software. The other cube was kept in deep freezer (−76°C) for a minimum of three weeks, followed by gamma irradiation and subjected to similar tests.

Results:

Results were compared in pre- and post-processed bone specimens. A significant loss of biomechanical strength (P<0.001) with mean a loss of 18.90 per cent was found in post-processed samples in uniaxial compression tests. Similarly, BMD (mean decrease by 13.8%, P<0.01) and histomorphometric indices such as Tb. T. (mean decrease by 12.37%, P<0.01), Tb. S. (mean increase by 12.60%, P<0.001) and B.V. (mean decrease by 20.84%, P<0.01) were found. However, Tb. N. was not significantly affected.

Interpretation & conclusions:

The current method of processing of bone allografts i.e. deep-freezing and gamma irradiation appeared to cause a significant reduction in the biomechanical strength of allogenic bone which was more suitable to be use in the morselized form. Appropriate consideration for decreased strength needs to be given when using allogenic bone graft as a structural graft.

Radiation sterilization of tissue allografts: A review

Tissue substitutes are required in a number of clinical conditions for treatment of injured and diseased tissues. Tissues like bone, skin, amniotic membrane and soft tissues obtained from human donor can be used for repair or reconstruction of the injured part of the body. Allograft tissues from human donor provide an excellent alternative to autografts. However, major concern with the use of allografts is the risk of infectious disease transmission. Therefore, tissue allografts should be sterilized to make them safe for clinical use. Gamma radiation has several advantages and is the most suitable method for sterilization of biological tissues. This review summarizes the use of gamma irradiation technology as an effective method for sterilization of biological tissues and ensuring safety of tissue allografts.

Current status of bone graft options for anterior interbody fusion of the cervical and lumbar spine

Anterior cervical discectomy and fusion (ACDF) and anterior lumbar interbody fusion (ALIF) are common surgical procedures for degenerative disc disease of the cervical and lumbar spine. Over the years, many bone graft options have been developed and investigated aimed at complimenting or substituting autograft bone, the traditional fusion substrate. Here, we summarise the historical context, biological basis and current best evidence for these bone graft options in ACDF and ALIF.

Adverse reactions and events related to musculoskeletal allografts: reviewed by the World Health Organisation Project NOTIFY

PURPOSE

The use of bone and connective tissue allografts has grown rapidly and surpassed the use of autografts in many countries. Being of human origin, bone and tendon allografts carry the risk of disease transmission and complications have been reported. As part of the Project NOTIFY led by the World Health Organisation, an effort to improve recognition, reporting, tracking and investigation of adverse outcomes of allografts was initiated, achieving a comprehensive review of associated disease transmission and failures. Those involving the use of musculoskeletal allografts are reported here. A major objective is to involve orthopaedic surgeons in the improvement of the safe use of the musculoskeletal allografts.

METHODS

We reviewed the medical literature, requested reports from surgeons in selected professional organisations and informally surveyed tissue bank organisations and selected tissue bank professionals to discover reported and unreported cases of adverse outcomes. We analysed each case to decide the likelihood that the complication was truly allograft related.

RESULTS

The efficiency of the procedures involved in bone banking and bone and tendon allograft has improved significantly during the last three decades. The evolution of the incidence of reported adverse reactions and events reflects positively on the safety of transplanted tissues. Cases of bacterial and viral transmission by bone and tendon allografts occurred mainly with those that contained viable cells, were not processed to remove cells, or were not disinfected or sterilised. We documented cases of transmission of human immunodeficiency virus (HIV), hepatitis C virus (HCV), human T-lymphotropic virus (HTLV), unspecified hepatitis, tuberculosis and other bacteria. Reporting of these adverse outcomes has led to corrective actions and has significantly improved the safety of allograft use. However, it is probable that not all cases have been reported and investigated.

CONCLUSIONS

Considering the high quality standards achieved in many countries, the best approach for further improvement in the safety of allografts is through a systematic reporting of all serious adverse reactions and events in the context of a global biovigilance programme.

Inactivation of enveloped and non-enveloped viruses on seeded human tissues by gamma irradiation

Human tissue allografts are widely used in a variety of clinical applications with over 1.5 million implants annually in the US alone. Since the 1990s, most clinically available allografts have been disinfected to minimize risk of disease transmission. Additional safety assurance can be provided by terminal sterilization using low dose gamma irradiation. The impact of such irradiation processing at low temperatures on viruses was the subject of this study. In particular, both human tendon and cortical bone samples were seeded with a designed array of viruses and the ability of gamma irradiation to inactivate those viruses was tested. The irradiation exposures for the samples packed in dry ice were 11.6–12.9 kGy for tendon and 11.6–12.3 kGy for bone, respectively. The viruses, virus types, and log reductions on seeded tendon and bone tissue, respectively, were as follows: Human Immunodeficiency Virus (RNA, enveloped), >2.90 and >3.20; Porcine Parvovirus (DNA, non-enveloped), 1.90 and 1.58; Pseudorabies Virus (DNA, enveloped), 3.80 and 3.79; Bovine Viral Diarrhea Virus (RNA, enveloped), 2.57 and 4.56; and Hepatitis A Virus (RNA, non-enveloped), 2.54 and 2.49, respectively. While proper donor screening, aseptic technique, and current disinfection practices all help reduce the risk of viral transmission from human allograft tissues, data presented here indicate that terminal sterilization using a low temperature, low dose gamma irradiation process inactivates both enveloped and non-enveloped viruses containing either DNA or RNA, thus providing additional assurance of safety from viral transmission.

On the effect of X-ray irradiation on the deformation and fracture behavior of human cortical bone

In situ mechanical testing coupled with imaging using high-energy synchrotron X-ray diffraction or tomography is gaining in popularity as a technique to investigate micrometer and even sub-micrometer deformation and fracture mechanisms in mineralized tissues, such as bone and teeth. However, the role of the irradiation in affecting the nature and properties of the tissue is not always taken into account. Accordingly, we examine here the effect of X-ray synchrotron-source irradiation on the mechanistic aspects of deformation and fracture in human cortical bone. Specifically, the strength, ductility and fracture resistance (both work-of-fracture and resistance-curve fracture toughness) of human femoral bone in the transverse (breaking) orientation were evaluated following exposures to 0.05, 70, 210 and 630 kGrays (kGy) irradiation. Our results show that the radiation typically used in tomography imaging can have a major and deleterious impact on the strength, post-yield behavior and fracture toughness of cortical bone, with the severity of the effect progressively increasing with higher doses of radiation. Plasticity was essentially suppressed after as little as 70 kGy of radiation; the fracture toughness was decreased by a factor of five after 210 kGy of radiation. Mechanistically, the irradiation was found to alter the salient toughening mechanisms, manifest by the progressive elimination of the bone's capacity for plastic deformation which restricts the intrinsic toughening from the formation "plastic zones" around crack-like defects. Deep-ultraviolet Raman spectroscopy indicated that this behavior could be related to degradation in the collagen integrity.

Effects of (60)Co gamma radiation dose on initial structural biomechanical properties of ovine bone--patellar tendon--bone allografts

Gamma radiation is established as a procedure for inactivating bacteria, fungal spores and viruses. Sterilization of soft tissue allografts with high dose (60)Co gamma radiation has been shown to have adverse effects on allograft biomechanical properties. In the current study, bone-patellar tendon-bone (BPTB) allografts from 32 mature sheep were divided into two treatment groups: low-dose radiation at 15 kGy (n = 16) and high-dose radiation at 25 kGy (n = 16) with the contralateral limb serving as a 0 kGy (n = 32) non-irradiated control. Half of the tendons from all treatment groups were biomechanically tested to determine bulk BPTB mechanical properties, cancellous bone compressive properties, and interference screw pull-out strength. The remaining tissues were prepared, implanted, and mechanically tested in an acute in vitro anterior crucial ligament (ACL) reconstruction. Low-dose radiation did not adversely affect mechanical properties of the tendon allograft, bone, or ACL reconstruction compared to internal non-irradiated control. However, high-dose radiation compromised bulk tendon load at failure and ultimate strength by 26.9 and 28.9%, respectively (P < 0.05), but demonstrated no negative effect on the cancellous bone compressive properties or interference screw pull-out strength. Our findings suggest that low dose radiation (15 kGy) does not compromise the mechanical integrity of the allograft tissue, yet high dose radiation (25 kGy) significantly alters the biomechanical integrity of the soft tissue constituent.

Fresh-frozen vs. irradiated allograft bone in orthopaedic reconstructive surgery

The use of allograft bone is increasingly common in orthopaedic reconstruction procedures. The optimal method of preparation of allograft bone is subject of great debate. Proponents of fresh-frozen graft cite improved biological and biomechanical characteristics relative to irradiated material, whereas fear of bacterial or viral transmission warrants some to favour irradiated graft. Careful review of the literature is necessary to appreciate the influence of processing techniques on bone quality. Whereas limited clinical trials are available to govern the selection of appropriate bone graft, this review presents the argument favouring the use of fresh-frozen bone allograft as compared to irradiated bone.

Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3-21.8 kGy) and a moderate absorbed dose (24.0-28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.

BMP-7 and CBFA1 in allograft bone in vivo bone formation and the influence of gamma-irradiation

An initial study showed that morselized human bone grafts were osteoconductive and osteoinductive when implanted in nude rat tibial window defects, and 25 kGy of gamma-irradiation significantly reduced those properties. The mechanism of the osteoinductivity and the influence of gamma-irradiation required further investigation. In this study we assessed the paraffin sections of seven morselized human bone grafts implanted into rat tibial defects for 3 weeks after being treated with 0, 15, or 25 kGy gamma-radiation respectively. Osteoclast-like cell counting and protein expressions of bone morphogenetic protein-7 (BMP-7), core binding factor alpha1 (CBFA1), and proliferating cell nuclear antigen (PCNA) were investigated and the positive signals were quantitatively analyzed. More new bone formation was observed in the 0 and 15 kGy groups compared with 25 kGy groups. The newly formed bones were found mainly from the intact cortex into the defects bridged by the implanted grafts. A dense staining of BMP-7 and CBFA1 was noted in the osteoblast-like cells in those areas. The BMP-7 and CBFA1 staining was also seen in the cells surrounding the implanted grafts in the centre areas of the defects in distance from the intact cortex. Quantitative analysis of immunohistochemical staining of the centre areas of the defects showed that gamma-irradiation (15 and 25 kGy) significantly reduced the expression of CBFA1 and BMP-7. In conclusion, morselized human bone grafts may contain some factors, which induced osteoblast lineage differentiation and bone formation and gamma-irradiation damages those bone inducing factors.

Biomechanical strength of deep-frozen versus lyophilized large cortical allografts

OBJECTIVE

To compare biomechanical strength of deep-frozen versus lyophilized large cortical allografts.

DESIGN

In vivo transplantation studies performed in tibia of adult cats using 4 cm deep-frozen and lyophilized, gamma-irradiated allografts to bridge large cortical defect model.

BACKGROUND

Bridging large cortical bone defect is a challenging problem. Options include autografts, allografts, bioceramics and prostheses. Allografts provide a suitable option.

METHODS

Forty mature cats were used. A large defect (4 cm) was created in mid-diaphysis of right tibia. In 16 cats, cortical defect was reconstructed using deep-frozen allografts (-80 degrees C) with intra-medullary rodding. In another 16 cats, lyophilized, gamma-irradiated allografts were used. Observation periods include 8, 12, 16 and 24 weeks. The specimens were procured together with unoperated legs as controls. Mechanical testing was performed using a materials testing machine with torsion test device of up to 500 Nm at speed of 0.18 rpm. Parameters studied included maximum torque, torsional stiffness and energy of absorption.

RESULTS

Deep-frozen allografts did not reach 100% strength, achieving only 64% at 6 months. In marked contrast, lyophilized allografts were significantly weaker with only 12% maximum torque strength at 6 months. Lyophilized allografts were significantly weaker than deep-frozen allografts in all observation periods (p < 0.05).

CONCLUSION

Deep-frozen allografts did not reach 100% normal strength and were significantly weaker than non-vascularised autografts. Lyophilized allografts were significantly weaker than deep-frozen allografts.

RELEVANCE

For the reconstruction of massive cortical bone defects, only deep-frozen cortical allografts should be used. Lyophilized allografts are not suitable.

Effect of gamma irradiation on human cortical bone transplants contaminated with enveloped and non-enveloped viruses

In the production of bone grafts intended for transplantation, basic safety measures to avoid the transmission of pathogens are selection and serological screening of donors for markers of virus infections. As an additional safety tool we investigated the effect of gamma irradiation on the sterility of human bone diaphysis transplants and evaluated its impact on the virus safety of transplants. Model viruses were included in the study to determine the dose necessary to achieve a reduction factor for the infectivity titres of at least 4 log(10) at a temperature of -30+/-5 degrees C. The following viruses were used: human immunodeficiency virus type 2 (HIV-2), hepatitis A virus (HAV), and poliovirus (PV-1), and the following model viruses: pseudorabies virus (PRV) as a model for human herpesviruses, bovine viral diarrhoea virus (BVDV) for HCV, and bovine parvovirus (BPV) for parvovirus B19. A first approach was to determine the D(10) values (kGy) for the different viruses (virus inactivation kinetics: BPV 7.3; PV-1 7.1; HIV-2 7.1; HAV 5.3; PRV 5.3; BVDV <3.0 kGy). Based on these results, inactivation of these viruses was studied in experimentally contaminated human bone transplants (femoral diaphyses). For BPV, the most resistant one of the viruses studied, a dose of approximately 34 kGy was necessary to achieve a reduction of infectivity titres of 4 log(10). We therefore recommend a dose of 34 kGy for the sterilisation of frozen bone transplants.

Modern issues in bone graft substitutes and advances in bone tissue technology

Autogenous bone grafting is the gold standard in repair of bony defects, fracture nonunion, and promoting arthrodesis. The complications related to obtaining autogenous grafts can be significant, and numerous materials are now available for augmentation or substitution. Allograft materials are highly effective for most applications; however, the surgeon needs to be acutely aware of the source of the tissue, for some tissue banks still use unacceptable processing techniques that destroy the structural and osteoinductive capacities of the graft. DBM products are unregulated and serious concerns exist as to the distribution of inactive products as commercially available to the practicing surgeon. Pressure from the orthopedic community has caused some manufacturers to test their products for activity before distribution. Calcium-based ceramic materials are effective as osteoconductive agents and work well alone as bone void fillers; however, augmentation of these implants with osteoinductive materials should be considered for use in nonunions and arthrodesis. Composite materials that incorporate osteoinductive materials in osteoconductive scaffolds are promising. New technology in isolation and creation of recombinant human bone morphogenic proteins and growth factors, and in the application of autogenous stem cells are emerging as the future of bone grafting procedures.

The effects of processing and low dose irradiation on cortical bone grafts

The authors studied the effects of standard processing and preprocessing low dose gamma irradiation (1.5 Mrad) on the strength and incorporation of syngeneic and allogeneic cortical bone grafts. Bilateral femoral middiaphyseal 8-mm segmental defects in 120 male Fisher rats were stabilized with internal fixation. Each defect received one of six types of grafts: fresh syngeneic, processed syngeneic, irradiated processed syngeneic, fresh allogeneic, processed allogeneic, and irradiated processed allogeneic grafts. Graft processing included soaking in 70% ethanol and deep freezing for preservation. Irradiation was performed by 60Co source immediately before processing. Grafts were evaluated by histologic analysis, histomorphometric analysis, and biomechanical testing at 4 and 6 months after surgery. Graft treatment, either processing or irradiation processing, did not affect consistently or significantly the incorporation of syngeneic or allogeneic grafts. Graft allogenicity was the major determinant of the revascularization and the histologic pattern of graft incorporation. Processed and irradiated processed allogeneic grafts gained compressive strength with time and were as strong as syngeneic grafts at 6 months. Biomechanical and histologic data from this study suggest that standard processing and preprocessing low dose irradiation do not compromise the natural course of allogeneic cortical bone graft incorporation.

Allograft bone. The influence of processing on safety and performance

Advances in tissue processing technology have been important for the successful use of bone allografts. The challenge is to prepare allografts that are well cleaned, sterile, and free of viruses while still preserving the natural biologic and biomechanical properties of the tissue. This article discusses how processing techniques aimed at achieving safety and sterility can affect the properties vital for graft incorporation and healing.

Impaction allografting with cement for the management of femoral bone loss

Impaction allografting with cement is the only technique currently available which reverses the diminution of bone stock that occurs in a revision hip arthroplasty, and as such, has great potential. It is particularly appropriate in the younger patient, though older patients may also benefit from the technique. Although the short term results are encouraging, there is a need for further basic science research to determine the optimal graft material and prosthesis design. Refinements in surgical instrumentation and technique will continue to improve the predictability of the clinical result and expand the indications for this important addition to the available options in revision hip arthroplasty.